Calculate the volume of air required for the complete combustion of 2.5litres of methane gas.Air contains 20%by volume of oxygen. Assume that all volumes are measured under the STP.

Solution.

CH4 +2O2 produce CO2 + 2H2O
1VOL 2VOL 1VOL 2VOL
2.5L 5L
SUPPOSE THE VOLUME OF AIR=X
According to question
X of 20% =5L
Or, X×20/100 =5L
Or, X =25L
Hence,volume of air required for the complete combustion of methane is 25Litres.